http://jqyzxhjk6psc6ul5jnfwloamhtyh7si74b4743k2qgpskwwxrzhsxmad.onion/docs/torbutton/en/design/index.html.en
Of course, the distribution
among these sets are not uniform, but scaling by 50 will improve the situation
due to this non-uniformity for users in the less common resolutions.
Obviously the ideal situation would be to lie entirely about the browser
window size, but this will likely cause all sorts of rendering issues, and is
also not implementable in a foolproof way from extension land.